Railroads use switches to change railcars from one set of rails to another set of rails while the railcars are moving along the rails. A switch has stationary rails and movable rails that are located between the stationary rails. The movable rails are “point rails.” The stationary rails are “stock rails.” The point rails direct a railcar through the switch onto one set of rails or the other set of rails. In a switch, the point rails are tapered rails that move laterally in plane with the stock rails. The point rails may move between two, or in some cases more, positions to direct a railcar onto a set of rails. The switch may have a straight “through” track (i.e., the main line) and a diverging track. The diverging track may be a left-hand diverging track or a right-hand diverging track. The approach track (i.e., the set of rails before the switch) has a left rail and a right rail. The left rail and right rail of the approach track may both be continuous through the switch and may be the stock rail for both the through track and the diverging track. For example, in a right-hand diverging switch, the left rail of the approach track may continue straight and may be the stock rail for the through track. The right rail of the approach track may diverge to the right and be the stock rail for the right-hand diverging track.
The left point rail and right point rail may be mechanically locked relative to one another such that the point rails move simultaneously and maintain a consistent distance from one another. The point rails may move together such that only one of the point rails may be adjacent or “connected” to one of the stock rails at a time. The wheels of a railcar follow the connected point rail and the stock rail that is disconnected from the point rails. In the right-hand diverging switch example, the left point rail may be connected to the left or through stock rail while the right point rail may be disconnected from the right or diverging stock rail. The wheels may follow the diverging track. Conversely, if the point rails are moved such that the left point rail is disconnected from the through stock rail and the right point rail is connected to the diverging stock rail, the wheels of a railcar truck may follow the through track.
The switch may be operated by a switchstand or a switch machine. The switchstand or switch machine may be located on the left side or the right side of the switch. The switchstand or switch machine may be located on the through side of the switch or on the diverging side of the switch. The switchstand or switch machine may be connected to the switch mechanically to move the point rails. The location of the switchstand or switch machine may change due to the location and/or orientation of the switch relative to other structures or natural features. For example, a station may contain many rail lines that may interconnect or simply cross in a multitude of directions.
The rails, both stock and point, are supported by a railroad tie that distributes the weight of the rail and the cars across a larger area and into the ground. The tie may have a rail plate affixed thereto to allow the securement of the rail to the tie. Construction or repairs at a station may result in modifications to planned or existing designs for a switch direction or a switchstand or switch machine location. Alteration of the switch direction or switchstand or switch machine location in a conventional switch may require replacement of the tie and/or the rail-plate with a new tie and/or new rail plate specific to the new configuration.